The increasing miniaturization of electrical devices together with the often conflicting requirements for high volume, mass production at low manufacturing and applied cost but with zero defect, place exacting demands on connectors and associated circuitry.
In electrical connectors having loose-piece stamped and formed metal contacts assembled in plastic housings, the individual contacts must each be securely located by insulating wall portions on the housings. However, a change in contact size or pitches usually necessitates a different configuration of insulating wall portions requiring construction of different molds even when the outside configuration of the housing remains the same. A range or family of connectors with different contact pitches is therefore expensive to manufacture.
In one known connector shown in FIGS. 21 and 22, a male and female housing 50 and 51, respectively, comprise a longitudinally moveable male contact 52 of stiff, or hard material, such as a metalized fiberglass circuit board, advanceable through a housing mouth 54, and a pair of film circuits 53 arranged in face-to-face relation in alignment with a housing mouth 55. The film circuits have leading ends 57 secured around a cylindrical body of metal loaded elastomer 58 located in a housing compartment adjacent the mating face. The rigid male contact body with hard contacts is advanced through the mouths 54 and 55 and enters between the film circuits urging them apart with the resultant resilient deformation of the elastomer 58 effecting a contact force between the individual circuit plates on the film circuits and the board.
Disadvantages arise, however, from the non-flexible nature of the board permitting, only vertical or horizontal installation of the connectors they cannot be stacked, while exposed glass fibers and rough sheared corners of the metal contacts can scarify the film circuit surfaces, particularly during mating and unmating movement thereby limiting the number of reconnections that are possible.
Furthermore, variations in thickness of the board arising from poor manufacturing tolerances and warpage, cause variations in contact pressure increasing the risk of a poor or unreliable electrical connection.
In another known connector disclosed in Japanese Patent Publication 40-2588, reliance for contact pressure between engaging film circuits is placed on free end portions of walls of a channel section spring within which the film circuit extends in slack condition. However, for reliable contact pressure, the channel walls should be relatively long, precluding a connector structure of low height, while the slack condition increases risk of contact misalignment, particularly with tracks at desirably small pitch.
The invention concerns film circuit connectors which avoid or ameliorate at least some of the above-noted disadvantages.
According to one aspect of the invention, matable connector members each locate a film circuit extending in taut condition away from a mating face with one film circuit having a contact area extending across an elongate spring mounted parallel to the mating face, resilient depression of which spring urges contact areas of the respective film circuits together into electrical connection.
Preferably, the connector members are matable to bring the contact areas into face-to-face alignment with zero insertion force and an actuating element is provided on one connector for movement of the spring, providing the contact pressure.
The invention also provides a connector comprising an outer housing opening to opposite, mating and circuit board engaging faces, and a film circuit supporting member on which a film circuit is anchored, insertable through the board engaging face into the outer housing to locate the film circuit securely therein extending away from the mating face with a board connecting portion of the film circuit exiting from the board engaging face.
This arrangement affords easy assembly of the film circuit in the housing.
The invention further provides a film circuit connector in which conductive tracks on contact areas of the film circuit within a connector housing are of pre-selected, different widths and/or pitches (separation) according to desired electrical characteristics.
The invention also provides a film circuit connector in which conductive tracks on contact areas of the film circuit within the connector housing are of less width and pitch than corresponding portions of such conductive tracks on circuit board engaging areas of the film circuit outside the connector housing, facilitating alignment for connection to respective individual conductive tracks of the circuit board.
According to a further aspect of the invention, an electrical connector includes a matable insulating housing assembly, a film circuit supported thereby having a contact area therein for electrical connection with a contact body of a mating connector and, an external circuit board engaging portion, areas of the film circuit adjacent the board engaging portions being clamped by the housing to exit therefrom inclined towards the circuit board so that the board engaging portions will be resiliently flexed against the circuit board when the connector is mounted thereon.
Preferably, free end portions of film circuit conductors or tracks are stripped of the insulating web to provide the resiliently flexed board engaging portions enabling direct connection to respective conductive pads of the circuit board when the connector is mounted thereon.
Another problem arising when connecting conductive tracks of, a film circuit to a circuit board using a reflow solder technique is that, on reflow, solder can be squeezed from the location of the solder pads across the board by pressure applied during reflow to the engaging surfaces to be connected, causing short circuiting solder bridges between adjacent conductive tracks.
According to an additional, separate, aspect of the invention a board engaging portion of a film circuit has apertures formed through the insulating web thereof exposing lower surfaces of discrete portions of conductive tracks to the web face thereby providing pockets for receiving and confining the reflow solder pads therein during reflow.
Thus, both the risk of solder bridges is avoided and the accurate and stable location of the film circuit on the circuit board assisted by receipt of the individual solder pads respective pockets, affording low applied cost.
The invention includes the apertured film circuit per se and the technique of connection thereto using the reflow process.